The wireless telecommunications industry has been growing steadily for a number of years. Consumers continue to demand more coverage, faster access and improved functionality of wireless devices. The advent of data (in addition to voice) has taxed the ability of current networks to support the increased traffic and wireless Carriers are deploying newer, larger and more complex antennas and equipment to increase capacity. This affects both new and existing sites.
New sites are designed to support the larger and heavier equipment—but building new sites is very expensive and is usually done as a last resort and only when coverage areas are to be extended. The more common practice is to use existing sites and to simply replace equipment and antennas as needed. However, existing sites were not always designed for the lateral loads caused by the wind forces on the additional equipment and the supporting monopole must be augmented structurally to allow for these larger antennas and equipment.
A common type of tower built in densely populated urban areas is the monopole. These monopoles are usually multi-sided or round tapered or straight tubular structures with a very small profile and hence more attractive from a zoning and siting approval standpoint. However, these are also the more difficult to augment or modify structurally since the bolting of additional structural elements must be done from the outside as they are too narrow to access from the inside.
One of the more common methods of strengthening these monopoles has been the addition of flat plates or bars to the “flats or flat sides” of the multi-sided structures. Similar concepts are used for cylindrical structures. While this is fairly simple using bolts that can be installed from the outside, the magnitude of the forces seen in the flat plates or bars require very large quantities of bolts at the splice connections between the flat plates or bars for load transfer. For example, a typical splice requires the use of eighteen or more splice bolts per splice per reinforcing plate. Thus, a four-sided plate augmentation design would require seventy-two bolts at each splice elevation. Reinforcing a monopole from the ground to a one-hundred twenty foot elevation may require five or more splices, resulting in more than four-hundred bolts and four-hundred bolt holes to be drilled in the air in the field. As may be appreciated, drilling bolt holes into the monopole and installing such flat plates at elevated heights can be very costly and labor intensive.
As wireless networks continue to tax the structural capacity of existing monopole structures structural augmentation of these structures with flat plate reinforcing solutions will continue.